Critical Dimension (CD) line width metrology relates an intensity signal produced from a line width metrology device, such as a scanning electron microscope, to the actual size or scale of a patterned feature, such as a photoresist feature produced on a semiconductor layer. The intensity signal is visualized and manipulated as a signal, profile or, e.g., an amplitude modulated waveform signal. A measurement of the size (scale) of a patterned feature involves the extraction of edge positions from the waveform signal. Traditional line width metrology known to those skilled in the art ignores much of the effect caused by the variation of the shape of the patterned feature. However, the shape must often be determined because the shape has adverse effects on further processing of a semiconductor wafer.